The invention relates to a passive heat exchange apparatus which uses solar energy or the temperature differential between the outside environment and an enclosed region to provide either heating or cooling for that region. This region could be either the interior of a home or factory, or it could alternatively be a water heater or cooler.
Heating and cooling devices powered either by fossil fuels of electricity generated from fossil fuels are necessary in almost every habitation. However, as the world supply or fossil fuel dwindles, alternative sources of energy are becoming increasingly important in order to preserve the remaining supply of fossil fuels as long as possible. The use of solar energy is one such alternative. The widespread use of solar heating and cooling devices including the present invention would drastically reduce the demand for fossil fuels.
Solar heating or cooling in this type of device is generally accomplished by transfer of energy by radiation onto a panel, by conduction into a fluid adjacent the panel and by convection currents within tanks which have a structure permitting the convection currents to flow in one direction, but prohibiting flow in the reverse direction. Radiation to or from the unit effects the heat transfer. This uni-directional flow guarantees that the direction of heat flow into or out of the enclosed region will not be reversed by convection currents flowing in the opposite direction. A number of different solar heat exchangers have been developed. The patents to Meier, U.S. Pat. No. 3,987,782, Stelzer, U.S. Pat. No. 2,484,127, and Barnett, U.S. Pat. No. 2,553,073, all disclose solar heat exchange devices with valves to prohibit the reverse flow of a heat-transfer fluid to prevent undesired heat transfers. However, the valves used in all of these devices are mechanical in nature, with moving parts that are susceptible to failure. The patents to Marchant et al, U.S. Pat. No. 2,693,939, Nilsson, U.S. Pat. No. 4,006,856, and Hay, U.S. Pat. No. 3,563,305, also disclose environmental heating and cooling systems using a convection process.
An article by Shawn Buckley, entitled "Thermic Diodes Solar Panels: Passive and Modular", discloses the use of solar energy in a heating and cooling system. In Buckley's system, convection currents carry a fluid, such as water, vertically in a thin layer through a first tank exposed to solar radiation which heats the fluid. The heated fluid passes through additional plumbing and a complex oil check valve in a second tank to a third tank separated from the first, which stores the heated fluid until the heat is transferred into a room, or through a heat exchanger to warm other fluids. The check valve prevents the reverse flow that occurs when the outside temperature becomes lower than the temperature in the storage tank, thereby dissipating the energy stored in the tank. This valve contains a layer of denser heat transferring fluid such as water, and a layer of less dense immiscible fluid such as oil floating upon the denser layer. A riser tube extends vertically into the oil layer so that as the water in the thin layer is warmed by the sun, pressure in the riser tube forces the water to flow out of the tube and settle back into the water layer, thereby permitting the water to circulate in one direction. When the outside temperature drops below the temperature of the storage tank, a convection current attempts to flow in the reverse direction, causing the water layer in a check valve to rise, thereby forcing oil partially down the riser tube. However, when the less dense oil has advanced a certain distance down the riser tube, the average density in the riser tube and the thin layer will balance the average density in the storage tank and the check valve, thereby stopping flow. By disconnecting and reversing to the check valve, the device will operate in the cooling mode.
The present invention makes a number of advances over the prior art. The three functions of energy absorption, energy storage and prevention of reverse convection currents are all performed within a single container This unique feature provides a number of significant advantages. The circulation of the convection currents in the present invention is greatly improved over the prior art. By merging the various functions into a single container, a circulation free of the restrictions typical of more conventional plumbing has been achieved. The lower density layer floats directly on the higher density layer in a single tank in contrast to the system of Buckley, so that the hydraulic pressures in the heat transfer fluid act directly rather than transferring the hydraulic pressures to a valve compartment. Also, the present invention greatly reduces the problem of joint and seam leakage, since first, the total length of seams around the one tank is much less than the total length of seams around the tanks of a multi-tank design of similar capacity, and second, inter-tank connections have been eliminated.
The Meier U.S. Pat. No. 3,987,782, discloses a single tank design with a check valve, but the valve, a bimetallic strip, is not so sensitive or effective as the fluid valve of the present invention, and the overall design of the present invention is much simpler, effecting a great reduction in cost.
A unique feature of the present invention is that it provides for switching between its heating and cooling modes by simply moving a lever. A number of advantages are also inherent in the use of a two-liquid valve. The absence of moving parts eliminates the possibility of mechanical breakdown. Also, the two-liquid valve is much more sensitive than its mechanical counterpart so that the slightest differential in temperature will cause convection currents to flow. A combination of the advantages of a two-liquid valve and the advantages of flexible conversion between heating and cooling inside a single tank make the present invention a truly unique advance over the previous convection type heat exchangers.
Several features further improve the efficiency of the present invention. A baffle placed near the valveless inter-connection between the energy absorption area and the energy storage area aids in maintaining the temperature differential between these two areas when fluid is not flowing over the valve, without impeding the flow of convection currents when fluid is flowing over the valve. If desired, a door or louver system can be pivotably mounted to the wall of the container in contact with the outside environment. The surface of the door or louver system adjacent to the water wall can be of reflective material so that when the door is in an open position, energy radiated from the device can be reflected away, in the cooling mode, and radiation can be reflected towards the device in the heating mode.
Many other objects and purposes will become clear from the following detailed description of the drawings.